Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$188.61	5.620%	$199.2099	$199.21	$199.20	$199.20
Purchase #2	$240.56	8.271%	$260.4567	$260.46	$260.45	$260.50
Purchase #3	$94.81	4.254%	$98.8432	$98.84	$98.85	$98.80
Purchase #4	$25.93	10.223%	$28.5808	$28.58	$28.60	$28.60
Purchase #5	$74.39	11.453%	$82.9099	$82.91	$82.90	$82.90
Purchase #6	$113.38	9.151%	$123.7554	$123.76	$123.75	$123.80
Purchase #7	$236.89	4.167%	$246.7612	$246.76	$246.75	$246.80
7 purchase totals =	$974.57		$1,040.5171	$1,040.52	$1,040.50	$1,040.60